The present invention relates to a system for testing the failure or satisfactory operation of a circuit having logic components, in which n components form a system of components marked 1 to n in a predeterinned manner. These components are interconnected, so that on one output the system has a logic state dependent on the failure or satisfactory operation state of the system and which is dependent on the failure or satisfactory operation state of each of the n components of the system. Each of the components of the system has at least one simulation input able to receive a signal simulating the failure or satisfactory operation of this component.
This test system can permit the study of electronic circuit incorporating a plurality of logic components, but by analogy, it can permit the study of the failure or satisfactory operation of e.g. a hydraulic circuit, whereof one or more components can be in the failure or satisfactory operation state. In this case, the hydraulics circuit is replaced by an electronic circuit having a plurality of logic components, whose operation is equivalent, by analogy, to that of the corresponding components of the hydraulic circuit.
In general, a circuit constituted by logic components has an output, whose logic state is dependent on the failure or satisfactory operation state of each of its components. As stated hereinbefore, said circuit can either be a real circuit, or a circuit simulating a circuit to be studied. Each of the components generally has an input connected to an output of another component of the circuit and an input which can receive a signal simulating the failure or satisfactory operation of said component.
The systems making it possible to test circuits of this type are generally complicated and costly, whilst being difficult to put into effect. They are generally constituted by a computer, which is connected to the circuit to be tested via an interface specific to each circuit. This type of system requires a special processing program for each circuit, so that the tests carried out can take a long time.
In the testing of circuits constituted by logic components, the Expert is accustomed to using a certain number of terms, as indicated below.
The section of a circuit consists of all the marks of the defective components of said circuit, such that if all the components are defective, the circuit is defective, whilst the other components of the circuit not forming part of the section operates satisfactorily.
The link of the circuit consists of all the marks of the satisfactorily operating components of the circuit, such that if all the components are operating satisfactorily the circuit operates in a satisfactory manner, all the other components of the circuit not forming part of the link being defective.
The order of a section or link is constituted by the number of marks of the so respectively defective or satisfactorily operating components describing the section or link.
The minimum section is a section such that it is impossible to find another configuration, by eliminating one or more defective elements from among those whose marks describe the section and which would make it possible to maintain the circuit in a defective state.
A minimum link is a link such that it is impossible to find another configuration by eliminating one or more satisfactorily operating components from among those whose marks describe the link and would make it possible to maintain the circuit in a state of satisfactory operation.
The minimum section with respect to the preceding order is a section such that it is not possible to find another configuration of said section by eliminating a single defective component from among those whose marks describe the section, whilst maintaining the circuit in a defective state.
In the same way, a minimum link with respect to the preceding order is a link such that it is not possible to find another configuration of said link by eliminating a single component which is operating satisfactorily from among those whose marks describe the link, whilst maintaining the circuit in a state of satisfactory operation.
When all the components describing a section of a circuit are defective, the circuit is defective.
This is followed by the definition of a critical failure state of a circuit, one or more critical components in a critical failure state, as well as a critical section.
The critical failure state of a circuit or a system is a failure state thereof, such that there is at least one component describing a section of said circuit or system which, when it is marked returns the circuit to a satisfactory operation state.
A critical component of a critical failure state is a component describing the corresponding section and which, when it is marked, makes it possible to restore the circuit to a state of satisfactory operation (said component being the only one to be marked at a given time).
It is pointed out that there can be several critical components for the same section and that a failure state corresponding to a section only containing critical components makes it possible to deduce that the section is minimal compared with the preceding order.
A critical section is a section corresponding to a critical failure state of the circuit or system. In the same way, it is possible to define a state of critical satisfactory operation of a system or circuit, one or more critical components in a critical failure state, as well as a critical link. The state of critical satisfactory operation of a circuit or system is a satisfactory operation state of said circuit or system, such that there is at least one component describing a link thereof which, when it is brought into the failure state, places the circuit or system in a failure state. A critical component of a state of critical satisfactory operation of a circuit or system is consequently a component describing a link of said circuit or system which, when it is brought into the failure state, makes it possible to bring the circuit into the failure state (said component being the only one to be brought into the failure state at a given time).
It is pointed out that there can be several critical components for the same links and that a satisfactory operation state corresponding to a link only containing critical components makes it possible to deduce that the link is minimal with respect to the preceding order. A critical link is one which corresponds to a critical satisfactory operation state of the circuit or system.
Finally, it is possible to define an incoherent circuit or system, i.e. a circuit or system in which it is possible to find failure states, such that by adding one or more defective components to said circuit or system, the latter is brought into a satisfactory operating state. The component is then called non-coherent or incoherent.
Apart from the disadvantages referred to hereinbefore (cost, complexity, difficulty in putting into effect), the known testing systems do not make it possible in a simple manner to determine whether a section or link is minimal with respect to the preceding order. Also, only the system described in French patent application Ser. No. 8,104,868, filed on Mar. 11th 1981 in the name of the present Applicant, makes it possible to determine whether a section or link is minimal with respect to the preceding order in the case of very complex systems.
This system as well as the other known systems which more particularly use computers, do not make it possible to determine a critical satisfactory operation or failure state for complex systems, if a section or link is critical and no matter what the critical component or components in said critical section or link. In addition, these systems do not make it possible to establish whether a circuit or system for complex systems is incoherent and which is or are the incoherent component or components.